Electromagnetic device



June 1 1926.

. 1,536,877 0. E. QUCKLEY I ELECTROMAGNETI G DEVICE 2 Sheets-Sheet 1 Filed April 4, 1924 UNDER NO TENSiON Patented June 3, s

curse YORK.

33251.; UiiRilllttzhEi" I Application April 43 This invention relates to electromagnetic structures and isuparticular to such structures making use of a magnetic merohsr of nickel-iron alloy having high permeability and low hysteresis loss.

It .is an object of the invention to decrease the hysteresis loss and to maintain high permeability in certain magnetic alloys in which high permeability may be developed. Other objects of the invention will appear from the following disclosure.

To attain the above mentioned object, sad in accordance with the preferred embodiment of the invention, there is provided a core or member of magnetic material for an electric coil or circuit, which material, consists of or comprises an alloy of nickel and iron in the proportions of 28 nickel and 21 iron, and the magnetic member is subjected to a constant tension during operation. v

It has recently been found that a nickeliron alloy of the proportions just mentioned,

when properly heat treated, has remarkably high permeability at low magnetizing forces coupled with l'iigh resistivity and low hysteresis loss. So marked are the desirable characteristics of this materialthat it hos already found Wide and, important app tions in the electrom a ill the permeability of iron 7 row magnetizing forces is around 300, that oil the new material is ordinarily from ten to twenty times as great and may be made still greater by careful treatment. The hysteresis loss per cubic centimeter per loop for which the limiting value of the induction is 5,000 c. g. s. units is around 200 ergs or less. By low magnetizing forces is those much less than a gauss. The highest permeability of the new material ordinarily is reached when the force is a small fraction of a gauss. These are the forces encountered in signalin so that this material is particularly valua is in the signaling field. The name permallo has been applied to this and similar nickel-iron alloys; For a more com plete description of these alloys sec U. g. application of {In Elmen, Serial No. 4T3,- 877,'filed May 31, 1921.

It has now been discovered that when such ahickel-iron alloy has been suitably heat treated and then placed under tension of the proper amount there is produced in it the following advantageous changes,

Brio. issues.

The permeability ot 'a low field strength iricre to 5: point Whom it hecomcs rclc;

tively stable with respect to the tension over certain range and the coercive force sud hysteresis loss fall to on almost negligible value-in certain instances to loss thou one quarter that of the some materiel when not strained. Furthermore, portions of the curve bwomc very straight and the view of the core of Fig. l with a portion broken sway and Figs. 3 and 4- are espionatorg curves.

1 efcrriug to Figs. 1 and 2 or the drawing which illustrate a schematic representation to show the principles involved there is provided a framework 1, from the top of which is suspended a magnetic coil struc- 2 This coil structure comprises a primsry Winding 3, a secondary Winding 4: and a tertiary Winding 5 upon the coach. The core 6 is of nickel-iron alloy in the form or fine Wires which may be, for example, five mils in diameter. These are assembled in parallel relation to form a cylindrical mass clamped at the extremities by clamping caps and 8. The upper clamping cap 7 is attached to the upper portion of the framework 1, While to the lower clamping cap 8 is attached a spring dynamometer, The movahle end of the spring of the dyuamometer is attached by means of a wire or cord to shaft 9 upon which it may be wound by handle 10. Ratchet 11 and pawl 12 hold the shaft 8 in position with a desired tension applied to the core 6. Fig. 2 is a top View of the core with a portion of the cap removed disclosing the upper ends of the Wires forming the core. A source 13 of alternating current is connected to the pri mary Winding 3. Source iii-represents any source of alternating cur-rent either sinusoidal or of more complex form, such as would be roduced for example, by a microphone and an alternating current generetor Working into the same circuit. A source of will meager produced by battery 14.- that the magnetizing force required to saturate the core will be exceeded during each cycle. In this way, modulation, detection, harmonic generation and other forms of distortion may be el fected.

While a two-coil transformer is disclosed, it is obvious that an auto-transformer would operate upon the same principle and that the transformation ratio of the primary and secondary of such auto-transformer may, in a limiting case, be unity. It is obvious,

also that the translating device 17 could be transferred from the secondary to the primary circuit if distortion rather than voltage or current transformation is desired.

By varying the relation between the di ameter and the length of the core in a Well known manner, the rangeof externally applied field over which the permeability remains substantially constant, may be varied at will, but, in each case, the hysteresis loss which is represented by the area of the hysteresis loop remains small.

What is claimed is 1. An electron'iagnetic structure comprising an electric circuit, a magnetic element in inductive relation thereto comprising an alloy of nickel and iron', and means for maintaining a constant tension in said mag" netic element of such value that the perinesbility is greater than if no tension were applied.

2. An electromagnetic structure comprising an electric circuit, a magnetic element in inductive relation thereto comprising an alloy of nickel and iron, and means for main; taining a tension in said magnetic element of such value that the permeability is high and relatively constant for a considerable range of tension.

3. An electroma; etic device comprising an electric winding and a core therefor of magnetic material comprising an alloy of nickel and iron which has high permeability of substantially constant value over a considerable range of tensile forces, and means for applying a substantiallyconstant tensile force within said range.

4. An electromagnetic device comprising an electric-Winding and a core therefor comprising a nickehiron alloy in the form of elements of small cross sectional area, and means for applyingtension to each'of said elements.

5. The combination with a member of magnetic material comprising nickel and iron which when placed under tension of a certain range of values increases in permsability and at the same time decreases in hysteresis loss, with means for maintaining said member under constant tension within said range.

6. A magnetic element consisting of an alloy in which nickel constitutes about 78% and iron about 22%, and means for maintaining said element under tension.

7. A magnetic element which abruptly approaches saturation at a levy tenths of a gauss field strength consisting of an alloy comprising nickel and iron continuously externally strained in the direction of the flux.

8. A. magnetic element, the flux of which varies substantially linearly with variations in field strength from near zero. value to a value at which the material approaches saturation consisting of an alloy comprising nickel and iron continuously externally strained in the direction of the flux.

9. A. magnetic element having acoercivity of the order of a hundredth that of iron consisting of an alloy comprising nickel and iron continuously externally strained in the direction of the flux.

10. A magnetic material having high pernieability at low magnetizing forces in combination with means for applying an elongating stress to the material whereby its permeability at low magnetizing forces is increased and its hysteresis loss deceased.

11. A magnetic clement consistingof an alloy in which nickel constitutes about 78% and 'iron about 22%,. and means for maintaining said element under a constant ten sion of approximately 5,500 pounds per square inch whereby the coercivity of the material is substantially lowered.

In witness whereof, I hereunto subscribe my name this 3 day of April A. 1)., 1924.

OLIVER E. BUCKLE? 

